We have prepared C14 tagged samples of the tetrapeptide, H-thr-pro-arg-lys-OH (TPAL) and the steroid-like compound under study. These will be used to determine site of action of each material. Hypothalamus, pituitary, ovary and plasma will be investigated in both cases. TPAL will be administered on day 2 to progravid hamsters and steroid on day 2 to non-bred hamsters. Analysis will use extracts of tissues and a complete counting cocktail. The new sample of synthetic TPAL from Diamalt will be tested for biological effectiveness as a contraceptive compound in mice and rats. The size of the embryonic "storage protein" for TPAL will be determined using lower range Sephadex- G-25 with standards of appropriate size, perhaps polystyrene markers. The naturally occurring steroid will be accumulated from the source tissue until sufficient is available for structural analysis. Purification of extracts is normally via thin-layer chromatography but attempts will be made using Sephadex LH-20. Whichever system is used, bioassay must be utilized for each "purified" sample to be certain of the active identity of the compound used for later analysis.